Die-cutting method, flexible abrasive product and apparatus for manufacturing thereof

ABSTRACT

The present invention relates to a method for manufacturing a flexible abrasive product, to such an abrasive product as well as to an apparatus for manufacturing the same. Hereby, the abrasive product is formed to be of the shape of a substantially regular polygon by die cutting it off a material strip. In the present case, the abrasive product has obtained a polygonal shape in which adjacent sides have a reciprocal interior angle of substantially 120 to 150°, whereby the die cutting is carried out in such a way that it coincides at least partly with the die cutting of several adjacent abrasive products. In this way, the die cutting can provide a partially continuous cutting line on the periphery of each individual abrasive product, which cutting line has a significant part of its length in common with the adjacent abrasive products.

BACKGROUND

The present invention relates to a method for manufacturing a flexible abrasive product of the kind presented in the preamble of claim 1. The invention further relates to a flexible abrasive product of the kind presented in the preamble of claim 11, as well as to an apparatus of the kind presented in the preamble of claim 16, intended for manufacturing such a flexible abrasive product.

In particular, the invention relates to what is called flexible abrasive and polishing discs used in rotating and oscillating work stages.

PRIOR ART

In die cutting various abrasive products, for example discs, a narrow material bridge is normally left over which binds together the waste material remaining between the die cut abrasive products. Thanks to such a material bridge, the waste material forms a continuous web that is easier to gather and remove from the die-cutting tool. On the other hand, such material bridges also bring about extra waste and affect thus not only the output of the material strip but also the handling of the waste material. The significant amount of waste material also has a negative effect on the price of the abrasive product, and the costs of the waste material handling rise

There have been attempts to decrease this waste material by placing the abrasive products to be die cut adjacent to each other to save material. It has, however, turned out that when attempting to cause two adjacent blades of a die-cutting tool to touch each other, or at least to reduce the material bridge between the abrasive products to a minimal string, the material strip will be wedged in between the blades of the die-cutting tool in the area where the blades are adjacent to each other. The blades must have a given thickness and their cutting edge has been shaped conical in the sharpening, due to which there is no inclination either on the abrasive product side or on the waste material side of the blade.

Die cutting flexible abrasive material is also difficult to carry out in a purely technical sense. There are several different reasons for this. First and foremost, the abrasive grains in the material strip quickly wear the die-cutting tool used for the work and make them blunt. The work requires thus continuous supervision and maintenance of the die-cutting tools.

Secondly, the backside of the material strip usually has a fastening layer of some kind. The fastening layer comprises either self-adhesive glue, velour cloth with loops, attached with glue, or loops of fiber integrated into the base material of the material strip. In the die cutting carried out to detach the abrasive product from the material strip, the loops, the self-adhesive glue as well as the protective film applied against the self-adhesive glue make the die cutting more difficult, because the remainders of the die cutting stick to the fastening layer and the material strip tends to stick to the die-cutting tool. Furthermore, it is very difficult to succeed in cutting off all tough fibers which the loops in the velour cloth is formed of or which the fibers integrated into the material strip generate, particularly because the die-cutting tools get blunt quickly due to the abrasive grains.

It is also difficult to place abrasive products close to each other, because it is purely generally difficult to obtain a pure cut in die cutting if another cuffing line is touched with far too small an angle. Herein lies a risk that the material strip will bend and the completion of the die cutting will be prevented.

Die cutting of the abrasive material is further made more difficult by the fact that the abrasive material must often also be provided with dust extraction openings, die cut on the surface of the abrasive material and divided more or less regularly thereto. There are often several dust extract openings, and they have a relatively small diameter. These dust extract openings are obtained with particular capsular punching means, i.e. what are called tube punchers, or by a type of cutting where a piston-shaped die-cutting means cooperates with an opening in the opposite cutting plate. Since the intention is to have clearance Inside the die-cutting means that cuts the dust extract opening, the tube puncher is structurally made substantially conical, whereby the abrasive product to be die cut tends get stuck to the surface of the die-cutting means because it is simultaneously cut loose from its place in the continuous material strip.

DEFINITION OF THE PROBLEM

With the present invention, the problems of known solutions can be substantially avoided. By applying the invention, waste material can be significantly decreased in manufacturing flexible abrasive products, at the same time as reliable die cutting with minimal defects is achieved.

This object is achieved in accordance with the invention by giving the method for manufacturing a flexible abrasive product the characterizing features of the characterizing part of claim 1. The flexible abrasive product is given the characterizing features of the characterizing part of claim 11, while the apparatus for manufacturing of such a flexible abrasive product is given the characterizing features of the characterizing part of claim 16.

The corresponding dependent claims that follow present suitable further embodiments and variations of the invention that further improve the functioning of the invention.

The invention is based on the idea that the amount of waste material can be reduced by deviating from the conventional circular shape of abrasive products used in rotating work stages, and by making the abrasive product polygonal instead, for example hexagonal, octagonal or dodecagonal. The greater the diameter of the abrasive product, the more corners may preferably be given to the product.

Thanks to the polygonal shaping, adjacent abrasive products can have common cuffing lines.

In the present invention, the “blade” refers to the working part of a cutting means, performing the cutting work. This blade provides hereby a “cutting line” in the material strip.

With the present invention, several significant advantages over the prior art are achieved. Hence, it is possible to reduce not only the amount of waste material but also the total length of the required cutting line by enabling the adjacent abrasive products to have common cutting lines.

This can be illustrated with a dodecagon. When placing abrasive products shaped as dodecagons in such a way that they abut on each other, they have half of the 12 sides in common with one of the adjacent dodecagons. This means that the total cutting line is reduced by 25%.

By deviating from the circular cutting line and replacing it with a broken line it is possible, at the same time, to increase the angle at the points where the cutting lines touch each other and to ensure clean cuts in the die cutting. In this way, bending of the material strip edge in the completion of the die cutting is avoided. In the die cutting of for example the above-mentioned dodecagons placed adjacent to each other, the intersection angle between the blades, where thy touch each other, is either 30 or 60 degrees, which is enough to obtain a clean cut as far as to the touching point of the out.

The die cutting of abrasive products can be simply improved further by dividing the die cutting process into two or more steps succeeding each other.

If the simpler angular geometry of the abrasive product is hereby combined with cuffing at the first die-cutting stage both possible dust extract openings in the abrasive product and principally those edges that are directed more in the feed direction of the material strip, the sticking of the abrasive product to the tube punchers is prevented, because the abrasive product still remains attached to the material strip. At the following die-cutting stage or feed position, the remaining continuous material bridges are cut off, whereby the abrasive product is cut out and detached. In practice, the whole material strip ceases to exist because the abrasive products have a large number of common edges, and the minimal geometric waste there is between, for example, dodecagonal abrasive products turn into separate loose pieces that can be sucked away with underpressure or that can drop into a collecting container where they are brought about.

The die-cutting tool does not need to be formed as a single piece either but can easily be divided into two or more parts because of the simple geometric shape. The geometric structure of the die-cutting tool is very simple and may preferably comprise straight blade parts and possible tube punchers or other punching tools.

Handling the finished abrasive products and possible waste material also gets simpler in die cutting with several parts. Thus, in the completion stage of the die cutting, the abrasive product can be gripped with a receiving apparatus before the abrasive product is completely detached from the material strip. Subsequently, the abrasive disc fixed to the receiving apparatus is cut off the material strip, so that it can be immediately after this transported to further treatment or other handling.

Further advantages and details of the invention become apparent from the description below.

BRIEF DESCRIPTION OF THE FIGURES

In the following, the invention is described in greater detail with reference to the drawing, in which

FIG. 1 shows part of a material strip, indicating the cutting lines for hexagonal abrasive products;

FIG. 2 shows part of a material strip, indicating the cutting lines for octagonal abrasive products;

FIG. 3 shows part of a material strip, indicating the cutting lines for dodecagonal abrasive products;

FIG. 4 show examples of a die-cutting sequence in manufacturing a hexagonal abrasive product;

FIG. 5 show examples of a die-cutting sequence in manufacturing an octagonal abrasive product; and

FIG. 6 show examples of a die-cutting sequence in manufacturing a dodecagonal abrasive product.

PREFERRED EMBODIMENTS

Some preferred embodiments of the present abrasive product, as well as the method and apparatuses for manufacturing thereof are described in the following with reference to the above figures. Hereby, the solution comprises the structural parts of the figures, each of which is denoted with a reference numeral corresponding to the reference numerals in the following description.

The figures thus show a flexible abrasive product, which is particularly intended for rotating and/or oscillating abrasion. The abrasive product comprises a flexible backing, to which a layer of abrasive agent is bonded with at least one glue layer on one side of the backing. On the opposite side of the abrasive agent, the abrasive product preferably has a fastening layer in the form of a glue layer, for example. The fastening layer can also comprise a velour layer or loops applied to the backing to contribute to Velcro fastening.

Such abrasive products are usually manufactured by die cutting them out of a particular material strip 1 with one or more die cutting tools, whereby the abrasive product 2 is both detached from the material strip and provided with possible dust extract openings 3. As can be seen from the attached figures, the present abrasive product is a polygon. Preferably, it is a regular polygon with an even number of sides. The polygon shape encompasses particularly abrasive products whose adjacent sides have a reciprocal interior angle of substantially 120 to 150°, whereby the number of corners is for instance 6, 8 or 12, which also corresponds to the geometric shapes hexagon, octagon and dodecagon. Distribution of a hexagonal abrasive product in the material strip is schematically shown in FIG. 1, while distribution of an octagonal abrasive product is shown in FIG. 2 and of a dodecagonal abrasive product in FIG. 3. Naturally, the magnitude of the interior angle or the number of corners of the polygon may be greater than in the above example.

A dodecagonal version can in fact be considered a hexagonal one in which the corners have been cut off. It means that there may be versions that are dodecagons where every other side is shorter than the six sides that are shared with the adjacent abrasive product. The symmetry is then only hexagonal. If one goes as far as to 16-angled products, the advantage of the shared cutting line decreases, and also the intersection angle decreases. Thus, when one approaches the circular shape, the effect of the idea is significantly deteriorated.

When implementing the die cutting of the abrasive products 2 in accordance with FIGS. 1 to 3 in such a way that the die cutting provides a partially continuous cutting line 4 on the periphery of each individual abrasive product, at least part of the sides of adjacent abrasive products meet. Such shaping in the die cutting minimizes the total extension of the cutting lines and maximizes the use of the material strip, still creating an abrasive product that is well applicable to rotating and/or oscillating abrasion.

For the most part, the cutting line obtained in the die cutting is substantially rectilinear, whereby its total length is less than the length of the cutting line in a conventional circular abrasion disc, but in special cases the sides that are not shared may be bent. As an example, the side of the polygon is substantially of the shape of a circular line with a diameter greater than the nut-formed perimeter of the shared sides, for example equal to the diameter of the circumscribed circle of the polygon

Thus, an abrasive product 2 is formed which is of the shape of a substantially regular polygon by means of die cutting in such a way that the die cutting at least partly coincides with the die cutting of several adjacent abrasive products. Selecting the shape of the abrasive product to be hexagonal or dodecagonal provides a die cutting method where six of the sides are always shared. This means that in the die cutting of a hexagonal abrasive product a utilization degree of nearly 100% is achieved for the material strip. If, on the other hand, octagonal abrasive products are die cut, about 1/7 of the total length of the sides is shared.

To simplify the work process and to facilitate the handling of the abrasive products 2 with the die cutting completed, the die cutting may take place in two or more strokes, preferably in such a way that the die cutting takes place in two successive work stages. By die cutting at the first stroke both possible dust extract openings 3 in the abrasive product and, for the most part, those edges that are directed more in the feed direction of the material strip, a continuous material strip is maintained at the same time as the abrasive product is prevented from sticking to the tube punchers or corresponding die cutting means used in shaping dust extract openings. Since the abrasive product partially sticks to the common material strip, it is prevented from getting stuck in the die cutting means and being carried along with it.

At the following stage of the die cutting, i.e. in the feed position, the remaining material bridges joining the abrasive product 2 to the material strip 1 are cut off, which results in the abrasive product being cut out and detached completely from the surrounding material. In practice, it can be said that the whole material strip ceases to exist. This is because the abrasive products and the possible minimal geometric waste 5 between the abrasive products turn into separate loose pieces without any connecting material bridges. Subsequently, the waste material can be sucked out with underpressure, or it can drop into a collecting container where the waste material is brought about.

The die cutting can also be explained with reference to the different abrasive products 2 in FIGS. 3 to 6. Thus, the material strip 1 is, by way of example, arranged to feed forward exactly the length of an abrasive product at every die cutting stroke. The die-cutting tool is thus divided to two work stages in such a way that it has, at its first work stage, blades that in the transportation direction (to the left in the figure) cut, for the most part, the longitudinal but also partially slanting sides in the abrasive product. These blades are illustrated in FIGS. 4 to 6 by blades 6 in row 1, column 1.

At the same time, possible punching of dust extract openings 3 of the abrasive product with blades 8 takes place in the form of tube punchers, for instance. These dust extract openings may represent any types of hole forms and hole standards. It is simple to die cut most different dust extract openings because the present die cutting with several strokes makes the die cutting easier.

At the second work stage die cutting of the remaining sides of the abrasive product takes place to cut the abrasive product 2 out completely. These blades 7 are, in turn, illustrated in FIGS. 4 to 6 by the blade on row 1, column 5.

The centre of the die cutting tool used at the second stage of the die-cutting is placed in a die cutting head at a distance from the centre of that part of the die-cutting tool which is used at the first stage of the die cutting, which is equal to or a multiple of the length of the abrasive product 2 in the transportation direction of the material strip 1. Therefore, the double length of the abrasive product is shown in the present figure. The two work stages are naturally successively after each other in the transportation direction of the material strip.

Division of the blades to adjacent rows is shown in rows 3 and 4, while the joint operation of the following work stages can be seen in rows 7 and 8.

To ensure that the abrasive product 2 is always detached from the material strip 1, the die cutting takes place with blades where adjacent or crossing cutting lines 4 somewhat overlap each other. Since the extent of such overlapping is insignificant, this will not, by any means, affect the use of the abrasive product.

In FIGS. 5 and 6, it can also be seen that the cutting line 4 required for detaching a side of the abrasive product can be generated by a blade divided into several parts. In this way, critical corner points are avoided in the die cutting, and instead, controlled overlapping with a complete cutting line is obtained as a result.

The die cutting sequences and blade divisions presented in FIGS. 4 to 6 are naturally only examples of different ways to carry out the die cutting. The blades can be divided also in other ways to achieve the desired result.

On the other hand, there are occasions when it is not desirable to detach the abrasive products 2 completely from each other. In such situations, the abrasive products are shaped to form a continuous chain via connecting parts between them. These may comprise, for example, incomplete cuts on adjacent sides of the abrasive product. When rows of successive abrasive products in a material strip are not die cut completely loose from each other, they can be simply packed by rolling them up into a roll or folded into a zigzag chain to facilitate transportation and later handling. In the die cutting of such continuous chains, the connecting part between the successive abrasive products preferably form a shared tear line weakened by the die cutting in such a way that the abrasive products can be easily detached from each other in further handling.

In order to manufacture a flexible abrasive product 2 of the above kind, a die cutting tool is advantageously used which comprises blades arranged to form substantially rectilinear cutting lines 4. These blades are further arranged to form the cutting line in such a way that when completed, the line is of the shape of a polygon. Further dividing the blades into at least two successive die cutting elements simplifies the die cutting process itself and guarantees complete through cutting. In such an embodiment, the blades arranged to provide a cutting line on adjacent sides of the polygon element may, for example, be arranged in different die cutting elements.

In its particular embodiment, the die cutting tool comprises two die cutting elements arranged to provide a cutting line 4 on the sides of the polygon in such a way that at the first die cutting stage the shared cutting lines of the adjacent abrasive products 2 are left uncut in the transportation direction of the material strip. At the same time, also at least one of the shared cutting lines in the cross-direction of the material strip 1 is left uncut. Thus, the continuous material strip and abrasive products provided by it can maintain their tension and shape in the forward feeding to the second die cutting stage, where the abrasive product is finally detached from the material strip.

To guarantee reliable detachment of the abrasive products 2 from the material strip and the adjacent abrasive products, the die cutting tool comprises blades arranged to provide cutting lines 4 that partly overlap each other. Furthermore, the die cutting tool also preferably comprises blades for die cutting of dust extract openings 3 in the abrasive product, i.e. what are called tube punchers, or the like die cutting means.

The die cutting tool may have different structures and thus comprise for instance a cutting plate and a blade holder with related blades or a cutting tool with a piston-like die-cutting part, which cuts against the edge of a corresponding groove when the piston-like part is pressed into the groove.

The above description and the related figures are only intended to illustrate the present abrasive product as well as the method and apparatus for manufacturing thereof. Therefore, the solutions are not restricted merely to the embodiments described above or in the attached claims, but a plurality of variations or alternative embodiments are possible within the idea described in the attached claims. 

1. A method for manufacturing a flexible abrasive product, which comprises a flexible backing, at least one glue layer on one side of the backing and a layer of abrasive agent bonded thereto by the glue layer, which abrasive product is formed to be of a shape of a substantially regular polygon by die cutting a material strip, characterized by giving the abrasive product a polygonal shape in which adjacent sides have a reciprocal interior angle of substantially 120 to 150° in such a way that the die cutting is carried out such that it coincides at least partly with the die cutting of several adjacent abrasive products, whereby a partially continuous cutting line is provided in the die cutting on the periphery of each individual abrasive product, which cuffing line has a significant part of its length in common with adjacent abrasive products.
 2. A method for manufacturing a flexible abrasive product according to claim 1, wherein in the manufacture of an octagonal abrasive product a peripheral cutting line is obtained that is common to the extent of 3/8.
 3. A method for manufacturing a flexible abrasive product according to claim 1, wherein in the manufacture of a hexagonal or dodecagonal abrasive product a peripheral cutting line is obtained that coincides with six of the sides.
 4. A method for manufacturing a flexible abrasive product according to claim 1, wherein the die cutting takes place at two or three stages.
 5. A method for manufacturing a flexible abrasive product according to claim 4, wherein the die cutting takes place at work stages following each other successively.
 6. A method for manufacturing a flexible abrasive product according to claim 5, wherein the die cutting takes place with two die cutting elements arranged to provide a cutting line on the sides of the polygon in such a way that in the first die cutting stage the common cutting lines are preferably left partially uncut in the transportation direction of the material strip, as is also at least one of the common cutting lines in the cross direction of the material strip, in order to maintain tension and shape in the material strip until the second die cutting, in which the abrasive product is finally detached from the material strip.
 7. A method for manufacturing a flexible abrasive product according to claim 4 wherein dust extraction openings are formed in the abrasive product at the first die cutting stage.
 8. A method for manufacturing a flexible abrasive product according to claim 1, wherein the die cutting takes place with blades such that crossing cutting lines somewhat overlap each other.
 9. A method for manufacturing a flexible abrasive product according to claim 1, wherein rows of successive abrasive products are formed in a material strip but are left therein not completely loose from each other, the abrasive products thus forming a continuous chain via connecting parts between them, the abrasive products being subsequently packed.
 10. A method for manufacturing a flexible abrasive product according to claim 9, wherein the connecting part between successive abrasion products comprising, in the forming of a continuous chain of abrasive products, a shared tear line weakened by the die cutting in such a way that the abrasive products can be easily detached from each other.
 11. A flexible abrasive product, which comprises a flexible backing, at least one glue layer on one side of the backing and a layer of abrasive agent bonded thereto by the glue layer, which abrasive product is of a shape of a substantially regular polygon and is die cut off a material strip, characterized in that the abrasive product has an even number of sides, whereby the polygonal shape encompasses abrasive products whose adjacent sides have a reciprocal interior angle of substantially 120 to 150°.
 12. A flexible abrasive product according to claim 11, wherein the number of sides is six.
 13. A flexible abrasive product according to claim 11, wherein the number of sides is eight.
 14. A flexible abrasive product according to claim 11, wherein the number of sides is twelve.
 15. A flexible abrasive product according to claim 11, wherein the abrasive product has dust extraction openings.
 16. An apparatus for manufacturing a flexible abrasive product, which abrasive product comprises a flexible backing, at least one glue layer on one side of the backing and a layer of abrasive agent bonded thereto by the glue layer, which abrasive product is arranged to be detached from a material strip with a die cutting tool, characterized in that the structure of the die cutting tool comprises blades arranged to generate substantially rectilinear cutting lines, whereby the blades are arranged to generate a cutting line which, when completed, is of the shape of a polygon.
 17. An apparatus for manufacturing a flexible abrasive product according to claim 16, wherein the blades are divided to at least two successive die cutting elements.
 18. An apparatus for manufacturing a flexible abrasive product according to claim 16, wherein the die cuffing tool comprises blades arranged to provide cutting lines which somewhat overlap each other.
 19. An apparatus for manufacturing a flexible abrasive product claim 16, wherein the die cutting tool comprises die cutting means for forming dust extraction openings in the abrasive product. 